Heretofore a luminescent type flat image display device, a plasma display, an EL display, fluorescent display tube, and a flat CRT have been known among other. However, the plasma display has a large in power consumption, the EL display has a low in the luminescence efficiency for the blue color, and the fluorescent display tube has a low in brightness in a full color display. By contrast, a system with luminescent cathodes has been known as a means for clearly and efficiently displaying color images, whereby the luminescent cathodes are part of a flat image display device. For example, flat panel display devices are shown in U.S. Pat. Nos. 4,028,582, 4,031,427, 4,088,920; 4,227,117; 4,622,497; 4,703,231; 4,736,139; and Japanese patent layed open publication Nos. 53-56961, 53-137665. Reinforcement partitions formed within an envelope for a picture display panel are shown in U.S. Pat. No. 4,622,492.
The conventional flat image display device, however, has the following problems.
1. It has been difficult to increase the resolution, and the colors tended to be uneven in a full color display.
2. The structure was complicated, and it was difficult to increase the screen size.
It has been difficult to obtain a high resolution because the brightness is modulated by the rows of back electrodes orthogonal to the linear thermal cathodes, and the electron beams emitted from the linear thermal cathodes toward the phosphor screen are spread widely. Particularly in the full color display, it is difficult for the electron beams to accurately energize the phosphors for each color of the three colors used, which results in an uneven color display.
The difficulty in increasing the size of the screen is due to the fact that the atmospheric pressure is applied to the evacuated thin-wall enclosure, that is, the strength of the enclosure is insufficient, whereby the enclosure is easily broken and it is difficult to manufacture.